“Written history began sometime around 3000 BC. . . .

Very early, a Sumerian who owned valuable resources (grain, or milk, or perhaps oil) would tie closed his bag of grain, smooth a ball of clay over the knot, and then press his seal on it. The seal, square or cylindrical, was carved with a particular design. When the ball of clay dried, the mark of the owner . . . was locked into the clay. The mark represented the owner’s presence. It watched over the grain while he was absent.”

—Susan Wise Bauer, The History of the Ancient World, 2007.